Hi all
Couldn't find last thread, so i'll start another. To review, I have a 98 convertible with engine dying from bad nikasil. currently in shop to check compression. Will possibly change plugs and at least one o2 sensor. All this to delay inevitable. I"ve been looking at engine replacement. The choices are stock used aj26, rebuilt aj26, aj27, or ls swap. Add the wild card of possibly a manual conversion. After researching this I've come to see that it's easier to do an ls swap than change to a newer jag engine. Apparently the whole wiring harness in the cars changed from 98 to 99 enough that one must choose mixing and matching the engine parts to changing the whole harness. Or, spend the money on a rebuilt aj26. I amazes me, that with the choice of creating a chevy lump, or keeping it jag, that no one has figured out the wiring, and/or controller changes to use a newer jag engine. I had, perhaps, foolishly, gotten a 2002 4.0 supercharged w/ trans from a running donor xjr with all the parts. Maybe it would be better to sell said same and get a rebuilt aj26 longblock.
Thanx'
Don

 

It is pretty amazing,,, til ya start thinking about it. And really frustrating. For the average guy, the considerations and CHANGES that would need to be made over the run of XK8 and associated changes make it almost impossible... I know, because I'm a very average guy.

I mean, these cars are soooo sensitive even when everything matches, and the early iterations and integrations (or the way they were done) of the CAN BUS and all that crap makes me feel like my cars are ticking time bombs sometimes.

Maybe if values and desirability INCREASE a fair amount folks will start creating durable, sensible and practical solutions to the many problems I see coming down the line as these cars age....? I dunno
It saddens me

 

Would be interested to know what Nikersil problems your are having and how they manifest themselves and of course your mileage.

 

Hi all'
pistnbroke, I've had this car for 9 years and I think it's been compromised from the moment I got it. When I had it to the dealer for a fuel pump(only time) the mechanic asked if I noticed it idled rough. I didn't know the difference. Recently, I had the chance to drive a 2000 conv. for a while and was surprised at the difference. Smoother idle, much more go. I changed plugs a few years ago and two of them had oil around
them. To me, the symptoms just add up to bad liners. That's why i have it in the shop to start out with a compression check and I'll go from there. I also got a code indicating a bad o2 sensor. It is original
but I'm sure the oil consumption isn't helping. That o2 sensor fail could account the for the current worsening of performance. To answer your mileage question, when i got car, i was getting 21mpg, last year18, now it's down to 14 and runs poorly. I'm hoping that, after some work, I can get it to run acceptably well for daily use again, but I believe the engines' days are numbered.
Thanx,
Don

 

It definitely needs properly working O2s and without that you can expect the sort of problems you mention.

Quite a cheap fix.

 

None of the things you mention point to the liners ...how many miles has it done not the MPG
Mine has piston slap at 112k

 

pistonbroke;
101,000 miles

 

Oil around the plugs indicates poor valve cover seals, not cylinder problems.

 

I went for a rebuilt when I replaced the one in my 1997 coupe last year. The car ran great with the new engine until I parked it for the winter. The rebuilt engine set me back just under $5k Canadian with shipping and the re and re at the mechanic was about the same. Hopefully the guys here can figure out your problem and it's an easier / cheaper fix for you.

 

Hi all;
I just got results from compression check. 175 in 5 cylinders, 125 in the other 3. What should i check next?
Thanks,
Don

 

Was that with oil or without ? Was the throttle wide open. If it was with oil then its probably ring related . If without oil then you need to do the bad ones with oil and see if it comes up.
Personally I dont check my conpressions as if it runs ok and does good gas mileage I dont worry.

You could get a borascope and have a look at the bores.....or put compressed air to the plug holes and see (listen) if it comes out exhaust or inlet .....???

 

1998 XK8 Jaguar Convertible with LS swap here & never regreted it.

Andrew from Jaguar Specialists makes a great kit for an LS swap: 1-408-839-5569

A LS Engine opens you to so many cool mods:
1) Turbo kit
2) Upgraded cam shaft kit adds 50 hp.
3) Upgraded carb

Only downside, the Jaguar judges subtract mad points at shows! 😠 😡

 

How about finding out the location of the three low bores. If all in a row, could be a head gasket and then see if the bad O2 sensor is on that bank.* The post compression test retest with oil is fairly standard for diagnostics. Was it done as asked above?

A leak-down test would help narrow it down.

You can get a dirt cheap cell phone borescope cable, aka endoscope cable, on ebay or Amazon. There are numerous free apps to download. The cell phone resolution is great and the image can be magnified with a whisk of 2 fingers. Cylinders will normally exhibit linear indications that can be from normal wear. Knowing which cylinders have good compression provides the benchmark for evaluating the weaker three.

* Is the O2 sensor bad or just the heater? What was the code? The defective heater will affect warmup but not influence running after warming up, it should go to closed loop.

 

You don't mention oil leaks, so I guess the car is using it rather than losing it? Oil consumption could be an indication of wear, but how much/often do you need to top up?

Re the compression figures, 175 sounds a little on the high side in theory for a normally aspirated motor with 10.75 CR. Bob (motorcarman) responded to a PM I sent him some time back re the Nikasil block: the figures we were discussing were all around the 125 mark. I'm sure he won't mind my repeating it here:

"
You can tell if there is a low or 'dead' cylinder by just the sound of the cranking.
All those look even but unless you get the engine 'up-to-temp', shut down and then check compression, the readings will likely be low like that.

The low tension of the rings in the nikasil engines need oil to seal. A cold engine should start with those readings and THEN once started, things EXPAND and then oil will probably help with the compression and the engine run normally.

As long as it does not smoke or blow oil into the full load breather and air filter box, it is probably a sound engine.
"

So definitely do a little more investigation before condemning the motor. My thoughts are that it would have died a long time ago if the Nikasil bores were already failing 9 years ago.

 

I'm not seeing anything that says Nikasil problem.

 

Hi all;
Wanted to update. I<m having a real adventure trying to get work done. I am operating on the idea that the engine can be at least made to run better. I cleaned the injectors. No significant difference. I use car at least once weekly to keep fresh.It runs somewhat rough under load and way down on power. To look from the other direction, what things would do this?, and what does bad cylinder linings act like?
Don

 

You haven't revealed fault codes from OBDII check. You are just playing guessing games without real feedback.

You can readjust Throtttle & Pedal Position sensors. If you have an OBDII scanner, it won't cost anything. https://www.jaguarforums.com/forum/x...ia-obd-264918/

There's no proof yet any problems are nikasil related. All supercharged engines had iron liners so you may have gotten a good deal. The next question is, will the heads & intake bolt onto the A27 short block. The reduced compression won't be an issue, other than enjoying tanking up with regular instead of premium. Having a spare trans isn't a bad idea, either.

 

+1

Not so, I'm afraid. All S/C motors up to 2000 MY were AJ26, and no AJ26 came out of the factory with steel liners. 2002MY should be fine in that respect, however engine # later than around 0008140900 would confirm (although it's likely to have Morse primary chaingear).


This thread from Jay111 will tell you what you need to know about AJ26/27 compatibilities, if you do arrive at that solution:
https://www.jaguarforums.com/forum/x...2/#post2496499

 

Faulty cylinder rings will cause a loss in power.

 

Hi all;
Will the aj26 na heads bolt on the 2002 supercharged block? Or would you change the cams? What about the intake manifold fit? I'm asking this because, as was suggested, I might be able to make use of the purchased engine if necessary without the host of problems, if I just use the block.
Thanx
Don